US8515591B2 - Device for estimating turning characteristic of vehicle - Google Patents

Device for estimating turning characteristic of vehicle Download PDF

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Publication number
US8515591B2
US8515591B2 US13/389,701 US200913389701A US8515591B2 US 8515591 B2 US8515591 B2 US 8515591B2 US 200913389701 A US200913389701 A US 200913389701A US 8515591 B2 US8515591 B2 US 8515591B2
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vehicle
yaw rate
value
stability factor
lateral acceleration
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US20120173040A1 (en
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Takahiro Yokota
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Toyota Motor Corp
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Toyota Motor Corp
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
    • B60W40/11—Pitch movement
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units, or advanced driver assistance systems for ensuring comfort, stability and safety or drive control systems for propelling or retarding the vehicle
    • B60W30/02—Control of vehicle driving stability
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W30/00—Purposes of road vehicle drive control systems not related to the control of a particular sub-unit, e.g. of systems using conjoint control of vehicle sub-units, or advanced driver assistance systems for ensuring comfort, stability and safety or drive control systems for propelling or retarding the vehicle
    • B60W30/18—Propelling the vehicle
    • B60W30/18009—Propelling the vehicle related to particular drive situations
    • B60W30/18145—Cornering
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
    • B60W40/112—Roll movement
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W40/00—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models
    • B60W40/10—Estimation or calculation of non-directly measurable driving parameters for road vehicle drive control systems not related to the control of a particular sub unit, e.g. by using mathematical models related to vehicle motion
    • B60W40/114—Yaw movement
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
    • B60W2050/0001—Details of the control system
    • B60W2050/0043—Signal treatments, identification of variables or parameters, parameter estimation or state estimation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W50/00—Details of control systems for road vehicle drive control not related to the control of a particular sub-unit, e.g. process diagnostic or vehicle driver interfaces
    • B60W2050/0062—Adapting control system settings
    • B60W2050/0075—Automatic parameter input, automatic initialising or calibrating means
    • B60W2050/0083—Setting, resetting, calibration
    • B60W2050/0088—Adaptive recalibration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2520/00—Input parameters relating to overall vehicle dynamics
    • B60W2520/12—Lateral speed
    • B60W2520/125—Lateral acceleration
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60W—CONJOINT CONTROL OF VEHICLE SUB-UNITS OF DIFFERENT TYPE OR DIFFERENT FUNCTION; CONTROL SYSTEMS SPECIALLY ADAPTED FOR HYBRID VEHICLES; ROAD VEHICLE DRIVE CONTROL SYSTEMS FOR PURPOSES NOT RELATED TO THE CONTROL OF A PARTICULAR SUB-UNIT
    • B60W2520/00—Input parameters relating to overall vehicle dynamics
    • B60W2520/14—Yaw

Definitions

  • the present invention relates to a device for estimating the turning characteristic of a vehicle and, more particularly, to a device for a vehicle which estimates a stability factor of the vehicle that represents the turning characteristic of a vehicle on the basis of a standard yaw rate of the vehicle and a transient yaw rate of the vehicle when the vehicle turns.
  • an actual yaw rate of a vehicle has a relationship of first order delay to a standard yaw rate of the vehicle and a coefficient multiplied to a vehicle speed in a time constant of the first order delay is referred to a time constant coefficient of steering response.
  • a stability factor of the vehicle and a time constant coefficient of steering response t represent a turning characteristic of the vehicle.
  • a stability factor of the vehicle and a steering-response-time constant coefficient can be estimated by using ARX (auto-regressive exogenous model) to estimate parameters a and b of a discrete-time transfer function from a standard yaw rate of the vehicle to an actual yaw rate of a vehicle.
  • a turning characteristic estimating device for a vehicle which estimates a standard yaw rate of a vehicle on the basis of running data when the vehicle turns; estimates parameters a and b of a discrete-time transfer function from a standard yaw rate of the vehicle to an actual yaw rate of the vehicle; estimates an estimation error ⁇ Kh of stability factor of the vehicle on the basis of the parameters a, b and vehicle speed V; and sets the sum of an initial value of stability factor and the estimation error ⁇ kh to an estimated value of stability factor of the vehicle.
  • the state values of a vehicle for calculating a standard yaw rate and an actual yaw rate are detected by sensors, the detected values of which can include detection error due to zero point offset of the sensors or the like. For that reason, in the conventional turning characteristic estimating devices such as that disclosed in the above-mentioned Laid-Open Publication, estimation of stability factor is liable to be affected by the detection error, which precludes enhancing estimation accuracy of stability factor.
  • the present invention provides a turning characteristic estimation device for a vehicle, wherein the device estimates a stability factor of the vehicle on the basis of the relationship between vehicle lateral acceleration removed of the components having frequency equal to or lower than a first predetermined value and yaw rate deviation index value removed of the components having frequency equal to or lower than a second predetermined value which is indexes the deviation between a transient yaw rate of the vehicle having a relationship of first order delay relative to a standard yaw rate of the vehicle and an actual yaw rate of the vehicle.
  • index value of deviation between a transient yaw rate of a vehicle involved in the relationship of a primary delay relative to the steady-state standard yaw rate of the vehicle and an actual yaw rate and lateral acceleration of the vehicle enables to estimate a stability factor of the vehicle on the basis of the relationship between a lateral acceleration of the vehicle and the index value of yaw rate deviation.
  • a stability factor of the vehicle is estimated on the basis of the relationship between vehicle lateral acceleration removed of the components having frequency equal to or lower than a first predetermined value and yaw rate deviation index value removed of the components having frequency equal to or lower than a second predetermined value. Accordingly, a stability factor can be estimated on the basis of vehicle lateral acceleration and yaw rate deviation index value which are reduced in steady detection error such as those due to zero point offset, whereby a stability factor can be estimated with higher accuracy than ever before.
  • the above-mentioned configuration may be such that: the device acquires information of vehicle lateral acceleration and yaw rate deviation index value over a plurality of times and estimates a stability factor of the vehicle on the basis of the relationship between an integrated value of vehicle lateral acceleration removed of the components having frequency equal to or lower than a first predetermined value and an integrated value of yaw rate deviation index value removed of the components having frequency equal to or lower than a second predetermined value.
  • the relationship between vehicle lateral acceleration and yaw rate deviation index value can be acquired irrespective of the phase difference between vehicle lateral acceleration and yaw rate deviation index value. Accordingly, a stability factor can be estimated with higher accuracy as compared with a case where a stability factor is estimated on the basis of the relationship between vehicle lateral acceleration and yaw rate deviation index value irrespective of the phase difference therebetween.
  • the above-mentioned configuration may be such that: the device calculates a first adjusting gain in accordance with the change degree of the estimated value of stability factor; sets a sum of a previous integrated value of vehicle lateral acceleration multiplied by the first gain and vehicle lateral acceleration acquired this time to the present integrated value of yaw rate deviation index value; and estimates a stability factor of the vehicle on the basis of the relationship between the present integrated value of vehicle lateral acceleration and the present integrated value of yaw rate deviation index value.
  • the integrated value of vehicle lateral acceleration and the integrated value of yaw rate deviation index value can appropriately be calculated in accordance with the change degree of the estimated value of stability factor. Accordingly, even when the change degree of the estimated value of stability factor is high, a stability factor can be estimated with higher accuracy as compared with a case where a first adjusting gain is not calculated in accordance with the change degree of the estimated value of stability factor.
  • the above-mentioned configuration may be such that: the device estimates a time constant coefficient of steering response which is a coefficient multiplied to a vehicle speed in a time constant of the first order delay on the basis of the relationship between transient yaw rate of the vehicle and actual yaw rate of the vehicle so that transient yaw rate of the vehicle approaches actual yaw rate of the vehicle; calculates a second adjusting gain in accordance with the change degree of the estimated value of time constant coefficient of steering response; sets a sum of a previous integrated value of vehicle lateral acceleration multiplied by the second gain and vehicle lateral acceleration acquired this time to the present integrated value of vehicle lateral acceleration; sets a sum of a previous integrated value of yaw rate deviation index value multiplied by the second gain and yaw rate deviation index value acquired this time to the present integrated value of yaw rate deviation index value; and estimates a stability factor of the vehicle on the basis of the relationship between the present integrated value of vehicle lateral acceleration and the present integrated value of yaw rate
  • a time constant coefficient of steering response is estimated on the basis of the relationship between transient yaw rate of the vehicle and actual yaw rate of the vehicle so that transient yaw rate of the vehicle approaches actual yaw rate of the vehicle. Accordingly, even when vehicle loading condition or the like varies, transient yaw rate of the vehicle can be calculated with higher accuracy as compared with a case where a time constant coefficient of steering response is set constant.
  • a second adjusting gain is calculated in accordance with the change degree of the estimated value of time constant coefficient of steering response and a sum of a previous integrated value of vehicle lateral acceleration multiplied by the second gain and vehicle lateral acceleration acquired this time is set to the present integrated value of vehicle lateral acceleration.
  • a sum of a previous integrated value of yaw rate deviation index value multiplied by the second gain and yaw rate deviation index value acquired this time is set to the present integrated value of yaw rate deviation index value. Accordingly, even when the change degree of the estimated value of time constant coefficient of steering response is high, a stability factor can be estimated with higher accuracy as compared with a case where a second adjusting gain is not calculated in accordance with the change degree of the estimated value of time constant coefficient of steering response.
  • the above-mentioned configuration may be such that: the device calculates a first adjusting gain in accordance with the change degree of the estimated value of stability factor; estimates a time constant coefficient of steering response which is a coefficient multiplied to a vehicle speed in a time constant of the first order delay on the basis of the relationship between transient yaw rate of the vehicle and actual yaw rate of the vehicle so that transient yaw rate of the vehicle approaches actual yaw rate of the vehicle; calculates a second adjusting gain in accordance with the change degree of the estimated value of time constant coefficient of steering response; determines a final adjusting gain on the basis of the first and the second adjusting gains; sets a sum of a previous integrated value of vehicle lateral acceleration multiplied by the final gain and vehicle lateral acceleration acquired this time to the present integrated value of vehicle lateral acceleration; sets a sum of a previous integrated value of yaw rate deviation index value multiplied by the final gain and yaw rate deviation index value acquired this time to the present integrated value of
  • a time constant coefficient of steering response is estimated on the basis of the relationship between transient yaw rate of the vehicle and actual yaw rate of the vehicle so that transient yaw rate of the vehicle approaches actual yaw rate of the vehicle. Accordingly, even when vehicle loading condition or the like varies, transient yaw rate of the vehicle can be calculated with higher accuracy as compared with a case where a time constant coefficient of steering response is set constant.
  • a stability factor can be estimated with higher accuracy as compared with a case where a final adjusting gain is not determined on the basis of the first and the second adjusting gains.
  • the above-mentioned configuration may be such that: the yaw rate deviation index values is calculated as a value in which the difference between transient yaw rate and actual yaw rate is transferred to steered angle deviation of the front wheels.
  • steered angle deviation of the front wheels is a difference between steered angle of the front wheels for achieving a transient yaw rate of a vehicle and an actual steered angle of the front wheels.
  • estimated value of a time constant coefficient of steering response can be derived on the basis of the yaw rate deviation index values which are not dependent on vehicle speed, so that a time constant coefficient of steering response can be estimated without being affected by vehicle speed.
  • the necessity can be removed to estimate stability factor of the vehicle in each vehicle speed.
  • the above-mentioned configuration may be such that: the device varies the first prescribed frequency and/or the second prescribed frequency according to an index value of the number of reciprocating steering operations by a driver per unit time.
  • the above-mentioned configuration may be such that: the device varies said first prescribed frequency and/or said second prescribed frequency according to an index value of the number of reciprocating steering operations by a driver per unit time.
  • Steady detection errors such as zero point offsets in detecting means for detecting state quantities of the vehicle and an actual yaw rate of the vehicle vary according to the number of reciprocating steering operations by a driver per unit time. According to the above-described configuration, steady detection errors can properly be removed in accordance with the number of reciprocating steering operations by a driver per unit time.
  • the above-mentioned configuration may be such that: the device varies the first prescribed frequency and/or said second prescribed frequency according to a magnitude of lateral acceleration of the vehicle.
  • Steady detection errors such as zero point offsets in detecting means for detecting such state quantities of the vehicle and an actual yaw rate of the vehicle vary according to the magnitude of vehicle speed change, i.e. the magnitude of longitudinal acceleration of the vehicle. According to the above-described configuration, steady detection errors can properly be removed in accordance with the magnitude of longitudinal acceleration of a vehicle.
  • the above-mentioned configuration may be such that: the device estimates a stability factor of the vehicle individually for clockwise turning and counter-clockwise turning.
  • a stability factor of the vehicle can be estimated for both clockwise turning and counter-clockwise turning even when turning characteristic differs according to turning direction of the vehicle for the reason, for example, that gravity center is not at the center in lateral direction of the vehicle or the position of gravity center varies so much in lateral direction of the vehicle.
  • the above-mentioned configuration may be such that: the device estimates a stability factor of the vehicle individually for each area of lateral acceleration of the vehicle.
  • the magnitude of a difference between transient yaw rate of the vehicle and actual yaw rate of the vehicle varies according to magnitude of lateral acceleration of the vehicle.
  • a stability factor of the vehicle can be estimated for each area of lateral acceleration, so that a time constant coefficient of steering response can be estimated without being affected by magnitude of lateral acceleration of the vehicle.
  • the above-mentioned configuration may be such that: the device adds an adjustment value of stability factor based on the relationship between the integrated value of vehicle lateral acceleration and the integrated value of yaw rate deviation index value to an initial value of stability factor utilized in calculation of the transient yaw rate of the vehicle to calculate the estimated value of stability factor.
  • the adjustment value of stability factor based on the relationship between the integrated value of vehicle lateral acceleration and the integrated value of yaw rate deviation index value is a correction value for correcting the value of the stability factor which was utilized in calculation of a transient yaw rate of the vehicle to approximate the estimated value of stability factor to a true stability factor. Accordingly, the estimated value of stability factor can be approximated to a true stability factor by correcting the value of the stability factor which was utilized in calculation of a transient yaw rate of the vehicle.
  • the present invention also provides a vehicle motion controller for executing a vehicle motion control utilizing a stability factor estimated by the device according to any one of claims 1 - 10 , wherein said vehicle motion controller varies a dead zone of said vehicle motion control in accordance with a convergence degree of the estimated value of stability factor.
  • a convergence degree of the estimated value of stability factor that is, the magnitude of the varying range of each estimated value corresponds to the accuracy in estimating a stability factor. According to this configuration, a dead zone of vehicle motion control can be changed in accordance with the accuracy in estimating a stability factor.
  • Cornering forces of a front vehicle wheel 100 f and rear vehicle wheel 100 r are denoted by Ff and Fr, respectively and Cornering powers of the front wheel and the rear wheel are denoted by Kf and Kr, respectively.
  • Vehicle speed V is now assumed to be constant and Laplace operator is denoted by s.
  • Laplace operator is denoted by s.
  • Kh in the above-described equation 9 is a stability factor and Tp in the above-described equation 10 is a coefficient multiplied to a vehicle speed V in a time constant of first order delay system having a time constant which is dependent on vehicle speed, that is, the coefficient referred to in this specification as “a time constant coefficient of steering response”.
  • These values are parameters which characterize a steering response in connection with yaw movement of a vehicle and represent a turning characteristic of a vehicle.
  • the above-described equation 8 is an equation for calculating a yaw rate ⁇ of a vehicle on the basis of actual steered angle of front wheel ⁇ , vehicle speed V and lateral acceleration Gy.
  • the yaw rate calculated from the linearized model is referred to as a transient yaw rate ⁇ tr.
  • the transient yaw rate ⁇ tr has a first order delay relationship relative to a steady-state standard yaw rate ⁇ t represented by the under-mentioned equation 11.
  • the above-mentioned configuration may be such that: a transient yaw rate ⁇ tr is calculated in accordance with the under-mentioned equation 11 corresponding to the above-described equation 8.
  • the deviation ⁇ t between a steady-state yaw rate ⁇ t and a detected yaw rate ⁇ during steady-state turning of the vehicle is represented by the following equation 13, in which designed value and true value of stability factor are denoted by Khde and Khre, respectively.
  • the steered angle deviation ⁇ t of the front wheels is one of the indexes of the deviation between a steady-state yaw rate ⁇ t and a detected yaw rate ⁇ and is not dependent on vehicle speed.
  • ⁇ t ( Khre ⁇ Khde ) GyL (14)
  • the steered angle deviation ⁇ t of the front wheels can be calculated as an index of the deviation between a steady-state yaw rate ⁇ t and a detected yaw rate ⁇ in accordance with the above-mentioned equation 14.
  • an estimated value Khp of stability factor can be calculated in accordance with the under-mentioned equation 15 by determining the relationship between a steady-state yaw rate ⁇ t and a detected yaw rate ⁇ , that is, an inclination (Khre-Khde)L of the relationship between vehicle lateral acceleration Gy and steered angle deviation ⁇ t of the front wheels on an orthogonal coordinate system with a least-squares method or the like.
  • Khp Khde +inclination/ L (15)
  • ⁇ 0 ⁇ KhdeGy 0 L While “ ⁇ 0 ⁇ KhdeGy 0 L” is constant, ⁇ 0 L/V changes according to vehicle speed V. Accordingly, the intercept of the axis of ordinate shown in FIG. 19 varies according to vehicle speed V. Therefore, when an detection error due to zero point offset in a sensor is included in the detected value of yaw rate ⁇ of the vehicle, the relationship of the steered angle deviation ⁇ t of the front wheels relative to lateral acceleration Gy varies according to vehicle speed V, which precludes to estimate stability factor accurately.
  • Vehicle lateral acceleration removed of the components having frequency equal to or lower than a first predetermined value is denoted by Gyft and yaw rate deviation index value removed of the components having frequency equal to or lower than a second predetermined value is denoted by ⁇ tft.
  • first and the second predetermined values are set to values which are sufficiently higher than varying speed of ⁇ 0 L/V according to the varying of vehicle speed V, Gyft does not include the error Gy 0 and ⁇ tft does not include errors due to the errors ⁇ 0 and ⁇ 0 . Accordingly, the following equation 18 corresponding to the above-mentioned equation 14 stands.
  • an estimated value Khp of stability factor can be obtained without being affected by the error due to zero point offset in sensors by determining the relationship between lateral acceleration Gyft and steered angle deviation ⁇ tft of the front wheels, that is, an inclination (Khre ⁇ Khde)L of the relationship between vehicle lateral acceleration Gy and steered angle deviation ⁇ t of the front wheels on an orthogonal coordinate system, and calculating an estimated value Khp of stability factor in accordance with the above-described equation 15.
  • the above-mentioned configuration may be such that: an estimated value Khp of stability factor is calculated in accordance with the above-described equation 15 in which the ratio of steered angle deviation ⁇ tft of the front wheels relative to lateral acceleration Gyft is denoted by inclination.
  • FIGS. 21 to 23 are graphs showing two time-series waves X, Y and a Lissajous curve of waves X, Y.
  • FIG. 21 is a graph for the case where there is no phase difference between the two time-series waves X, Y;
  • FIG. 22 is a graph for the case where the time-series wave Y lags the time-series wave X in phase;
  • FIG. 23 is a graph for the case where the time-series wave Y leads the time-series wave X in phase.
  • the above-mentioned configuration may be such that: an estimated value Khp of stability factor is calculated in accordance with the above-described equation 15 in which the ratio of the integrated value ⁇ tfa of steered angle deviation ⁇ tft of the front wheels relative to the integrated value Gyfta of lateral acceleration Gyft is denoted by inclination.
  • a first order delay filtering is conducted on steered angle deviation ⁇ tft of the front wheels and the integrated value ⁇ tfa thereof and a first order delay filtering is as well conducted on lateral acceleration Gyft and the integrated value Gyfta thereof. If the time constants in the first order delay filtering procedures are set to the same value, the inclination can be calculated on the basis of the first order delay filtered values as in a steady-state turning of a vehicle and the estimated value of stability factor can be calculated in accordance with the above-mentioned equation 15.
  • the above-mentioned configuration may be such that: the component equal to or lower than a first prescribed frequency is removed from a lateral acceleration by a high-pass filtering procedure and the component equal to or lower than a second prescribed frequency is removed from a yaw rate deviation index value by a high-pass filtering procedure.
  • the above-mentioned configuration may be such that: the first and second prescribed frequencies are same to each other.
  • the above-mentioned configuration may be such that: assuming vehicle speed is denoted by V and wheel base of a vehicle is denoted by L, the value in which a deviation between a transient yaw rate and an actual yaw rate is transferred to steered angle deviation of the front wheels is calculated by multiplying L/V to the magnitude of a deviation between a transient yaw rate and an actual yaw rate.
  • the above-mentioned configuration may be such that: the dead zone of the vehicle motion control is varied so that when the convergence degree of the estimated stability factor is high, the dead zone becomes narrow as compared with the case where the convergence degree is low.
  • FIG. 1 is a schematic diagram showing a first embodiment of a turning characteristic assuming device according to the present invention, the device being applied to a vehicle motion control device.
  • FIG. 2 is a flowchart showing a routine for calculating a stability factor Kh by estimation in the first embodiment.
  • FIG. 3 is a graph showing a relationship between a convergence degree Ckh of an estimated value of stability factor Kh and a reference value ⁇ o.
  • FIG. 4 is a flowchart showing a main portion of a routine for calculating a stability factor Kh by estimation in a second embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • FIG. 5 is a graph showing a relationship between steering frequency fs and a cutoff frequency fhc of a high-pass filtering procedure.
  • FIG. 6 is a flowchart showing a main portion of a routine for calculating a stability factor Kh by estimation in a third embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • FIG. 7 is a graph showing a relationship among steering frequency fs, a cutoff frequency fhc of a high-pass filtering procedure and an absolute value of longitudinal acceleration Gx of the vehicle.
  • FIG. 8 is a flowchart showing a main portion of a routine for calculating a stability factor Kh by estimation in a fourth embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • FIG. 9 is a flowchart showing former half portion of a routine for calculating a stability factor Kh by estimation in a fifth embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • FIG. 10 is a flowchart showing the latter half portion of a routine for calculating a stability factor Kh by estimation in a fifth embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • FIG. 11 is a flowchart showing former half portion of a routine for calculating a stability factor Kh by estimation in a sixth embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • FIG. 12 is a flowchart showing former the latter half portion of a routine for calculating a stability factor Kh by estimation in a sixth embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • FIG. 13 is a flowchart showing a routine for calculating a stability factor Kh by estimation in a seventh embodiment of the turning characteristic estimation device according to the present invention.
  • FIG. 14 is a graph showing a relationship between the absolute value of the deviation ⁇ Kh of stability factor and a lower limit value ⁇ amink of integrated value.
  • FIG. 15 is a graph showing a relationship between the absolute value of the deviation ⁇ Kh of stability factor and a lower limit value ⁇ Gyamink of integrated value.
  • FIG. 16 is a graph showing a relationship between the absolute value of the deviation ⁇ Tp of time constant coefficient of steering response and a lower limit value ⁇ amint of integrated value.
  • FIG. 17 is a graph showing a relationship between the absolute value of the deviation ⁇ Tp of time constant coefficient of steering response and a lower limit value ⁇ Gyamint of integrated value.
  • FIG. 18 is an explanatory diagram showing a two wheel model of a vehicle for estimating a stability factor.
  • FIG. 19 is a graph showing a relationship between vehicle lateral acceleration Gy and front wheels steered angle deviation ⁇ t.
  • FIG. 20 is a graph showing a relationship between vehicle lateral acceleration Gyft removed of the components having frequency equal to or lower than a first predetermined value and front wheels steered angle deviation ⁇ tft removed of the components having frequency equal to or lower than a second predetermined value.
  • FIG. 21 is a graph showing two time-series waves X, Y and a Lissajous curve of waves X, Y for the case where there is no phase difference between the two time-series waves X, Y.
  • FIG. 22 is a graph showing two time-series waves X, Y and a Lissajous curve of waves X, Y for the case where the time-series wave Y lags the time-series wave X in phase.
  • FIG. 23 is a graph showing two time-series waves X, Y and a Lissajous curve of waves X, Y for the case where the time-series wave Y leads the time-series wave X in phase.
  • FIG. 1 is a schematic diagram showing a first embodiment of a turning characteristic estimation device according to the present invention, the device being applied to a vehicle motion control device.
  • 50 denotes an entire vehicle motion control device for a vehicle 10 .
  • the turning characteristic estimation device according to the present invention is a part of the vehicle motion control device 50 .
  • the vehicle 10 has a right front wheel 12 FR, a left front wheel 12 FL, a right rear wheel 12 RR, and a left rear wheel 12 RL.
  • the right and left front wheels 12 FR, 12 FL which are steerable wheels, are steered by an unillustrated steering apparatus of a rack and pinion type via right and left tie rods 18 R and 18 L, respectively.
  • the steering apparatus is driven in response to steering operation of a steering wheel 14 by a driver.
  • Braking forces of the left and right front wheels 12 FL, 12 FR and the left and right rear wheels 12 RL, 12 RR are controlled through control of respective braking pressures of corresponding wheel cylinders 24 FL, 24 FR, 24 RL, 24 RR by a hydraulic circuit 22 of a braking apparatus 20 .
  • the hydraulic circuit 22 includes a reservoir, an oil pump, and various valve units, etc., although they are not illustrated. Pressure in each wheel cylinder is usually controlled by pressure in a master cylinder 28 driven by driver's operation of depressing a brake pedal 26 , and, as will be described below in detail, it is controlled as necessary by an electronic control unit 30 .
  • a steering column to which the steering wheel 14 is coupled is provided with a steering sensor 34 for detecting a steering angle ⁇ .
  • the steering sensor 34 , the yaw rate sensor 36 and the acceleration sensor 40 detect a steering angle, an actual yaw rate, and a lateral acceleration, respectively as positive values when the vehicle turns left.
  • the electronic control unit 30 are supplied with signals indicating pressures Pi detected by the pressure sensors 32 FR- 32 RL, a signal indicating steering angle ⁇ detected by the steering angle sensor 34 , a signal indicating actual yaw rate ⁇ detected by the yaw rate sensor 36 , a signal indicating longitudinal acceleration Gx detected by the longitudinal acceleration sensor 38 , a signal indicating lateral acceleration Gy detected by the lateral acceleration sensor 40 , and signals indicating wheel speeds Vwi detected by the wheel speed sensors 42 FR- 42 RL.
  • the electronic control unit 30 includes a micro computer having a CPU, a ROM, a EEPROM, a RAM, a buffer memory and input/output ports and these components are connected with one another by bi-directional common bus.
  • the ROM stores default values of stability factor Kh and time constant coefficient Tp of steering response which are utilized to calculate a standard yaw rate ⁇ t. These default values are set for each vehicle when it is shipped.
  • the EEPROM stores an estimated value of stability factor Kh and the like. As explained in detail hereinafter, the estimated value of stability factor Kh and the like are renewed by calculating them on the basis of running data when the vehicle is in turning condition.
  • the electronic control unit 30 calculates a steady-state standard yaw rate ⁇ t on the basis of turn running data such as steering angle and calculates a first order delayed transient yaw rate ⁇ tr by conducting a first order delay filtering utilizing the time constant coefficient Tp of steering response on the steady-state standard yaw rate ⁇ t.
  • the electronic control unit 30 calculates a front wheel steered angle deviation value ⁇ equivalent to yaw rate deviation which is derived by transferring the difference between a transient yaw rate ⁇ tr and an actual yaw rate ⁇ of the vehicle to a front wheel steered angle deviation.
  • the electronic control unit 30 calculates a first order delayed vehicle lateral acceleration Gyft by conducting a first order delay filtering utilizing the time constant coefficient Tp of steering response on the lateral acceleration Gy of the vehicle.
  • the electronic control unit 30 calculates a band-pass filtered vehicle lateral acceleration Gyftbpf and a band-pass filtered front wheel steered angle deviation value ⁇ bpf equivalent to yaw rate deviation.
  • the electronic control unit 30 calculates an integrated value ⁇ a of front wheel steered angle deviation value ⁇ bpf equivalent to yaw rate deviation and an integrated value ⁇ Gya of vehicle lateral acceleration Gyftbpf, and calculates an integrated value ratio ⁇ a/ ⁇ Gya.
  • the electronic control unit 30 calculates the sum of an initial value of stability factor Kh which is utilized in calculation of a steady-state standard yaw rate ⁇ t and an adjusting value based on the integrated value ratio ⁇ a/ ⁇ Gya as an estimated value of stability factor Kh. When a predetermined condition is satisfied, the electronic control unit 30 stores the estimated value of stability factor Kh in the EEPROM.
  • the electronic control unit 30 calculates a target yaw rate ⁇ tt corresponding to a transient yaw rate ⁇ tr using an estimated value of stability factor Kh stored in the EEPROM and calculates a yaw rate deviation ⁇ which is a difference between a detected yaw rate ⁇ and the target yaw rate ⁇ tt.
  • the electronic control unit 30 decides whether or not vehicle turning behavior is aggravated by judging whether or not the magnitude of the yaw rate deviation ⁇ exceeds a reference value ⁇ o (a positive constant). If the vehicle turning behavior is aggravated, the electronic control unit 30 controls the vehicle motion to stabilize vehicle turning behavior.
  • the vehicle motion control conducted by the electronic control unit 30 may be any control so long as it controls vehicle motion on the basis of the target yaw rate ⁇ tt which is calculated using an estimated value of stability factor Kh.
  • the electronic control unit 30 calculates a convergence degree Ckh of the estimated value of stability factor Kh.
  • the electronic control unit 30 variably sets a dead zone of the vehicle motion control by variably setting the reference value ⁇ o
  • Control according to the flowchart shown in FIG. 2 is started when an unillustrated ignition switch is turned on, and is repeatedly executed at predetermined time intervals. The same goes in the embodiments described hereinafter.
  • a stability factor Kh is initialized by setting the latest value renewed in step 190 in former vehicle running period to an initial value Kh 0 of stability factor Kh. It is to be noted that if there is no stored value of stability factor Kh in the FEEPROM, a default value which was set in advance when the vehicle was shipped is set to an initial value Kh 0 of stability factor Kh.
  • step 20 signals representing steering angle ⁇ , etc. detected by the associated sensors are read.
  • step 30 a low-pass filtering procedure is conducted on each signal indicating steering angle ⁇ , etc. to remove high frequency noise.
  • the low-pass filtering procedure may be, for example, a first order low-pass filtering having a cut-off frequency of 3.4 Hz.
  • step 40 vehicle speed V is calculated on the basis of wheel speeds Vwi; a steered angle ⁇ of the front wheels is calculated on the basis of steering angle ⁇ ; and a steady-state standard yaw rate ⁇ t is calculated in accordance with the above-mentioned equation 11.
  • a time constant coefficient Tp of steering response is set to its default value which was set in advance when the vehicle was shipped. It is to be noted that in the case where a time constant coefficient Tp of steering response is estimated on the basis of vehicle running data, a time constant coefficient Tp of steering response may be set to an estimated value.
  • step 60 a first order delay filtering utilizing the time constant coefficient Tp of steering response is conducted in accordance with the above-mentioned equation 12 to calculate a transient yaw rate ⁇ tr based on the steady-state standard yaw rate ⁇ t calculated in step 40 .
  • step 70 a first order delay filtering utilizing the time constant coefficient Tp of steering response is conducted on the vehicle lateral acceleration Gy in accordance with the under-mentioned equation 19 to calculate a first order delay filtered vehicle lateral acceleration Gyft.
  • Gyft 1 1 + TpVs ⁇ Gy ( 19 )
  • step 80 an equivalent value ⁇ converted to steered angle deviation of the front wheels is calculated in accordance with the under-mentioned equation 20, the value being derived by converting the deviation between the transient yaw rate ⁇ tr and the actual yaw rate ⁇ to the steered angle deviation of the front wheels.
  • step 90 high-pass filtering procedures are conducted on the first order delay filtered vehicle lateral acceleration Gyft which was calculated in step 70 and the equivalent value ⁇ converted to steered angle deviation of the front wheels which was calculated in step 80 to remove influences due to zero point offset in the sensors.
  • the high-pass filtering procedure may be, for example, a first-order high-pass filtering having a cut-off frequency of 0.2 Hz.
  • the above-mentioned high-pass filtering procedure Since the low-pass filtering procedure is conducted in step 30 as described above, the above-mentioned high-pass filtering procedure generates the results obtained by conducting a band-pass filtering procedure on the first order delay filtered vehicle lateral acceleration Gyft and the yaw rate deviation equivalent value ⁇ converted to steered angle deviation of the front wheels. Therefore, the vehicle lateral acceleration Gyft and the yaw rate deviation equivalent value ⁇ converted to steered angle deviation of the front wheels which were high-pass filtered in step 90 are referred to a band-pass filtered vehicle lateral acceleration Gyftbpf and a band-pass filtered yaw rate deviation equivalent value ⁇ bpf converted to steered angle deviation of the front wheels.
  • step 100 a decision is made as to whether or not the vehicle is under a turn running condition. If a negative decision is made, the control returns to step 20 . If a positive decision is made, the control proceeds to step 110 .
  • the decision as to whether or not the vehicle is under a turn running condition may be made by deciding whether or not the absolute value of lateral acceleration Gy of the vehicle is equal to or larger than a reference value, deciding whether or not the absolute value of actual yaw rate ⁇ of the vehicle is equal to or larger than a reference value, or deciding whether or not the absolute value of the product of actual yaw rate ⁇ of the vehicle and vehicle speed V is equal to or larger than a reference value, under the situation where the vehicle runs at a vehicle speed not lower than a reference value.
  • step 110 a decision is made as to whether or not adjustments are to be executed on the present integrated values ⁇ a of the band-pass filtered yaw rate deviation equivalent value ⁇ bpf converted to steered angle deviation of the front wheels and the present integrated values ⁇ Gya of the band-pass filtered vehicle lateral acceleration Gyftbpf calculated in step 130 in previous cycle. If a negative decision is made, the control proceeds to step 130 , while a positive decision is made, the control proceeds to step 120 .
  • a decision may be made that adjustments are to be executed on the integrated values ⁇ a and ⁇ Gya when either of the under-mentioned (A1) and (A2) is satisfied.
  • the condition (A2) is decided whether or not it is satisfied when a time constant coefficient Tp of steering response is estimated and a time constant coefficient Tp of steering response is se to the estimated value in step 50 .
  • an adjust gain Gaj is calculated in accordance with the under-mentioned equation 21, in which a lower limit value previously set for the integrated value ⁇ a of the band-pass filtered yaw rate deviation equivalent value ⁇ bpf is denoted by ⁇ amin (positive constant) and a lower limit value previously set for the integrated value ⁇ Gya of the band-pass filtered vehicle lateral acceleration Gyftbpf is denoted by ⁇ Gymin (positive constant).
  • MIN represents that a minimum value in the values in the bracket is selected and Max represents that a maximum value in the values in the bracket is selected. The same goes to the other similar equations.
  • Gaj MIN ⁇ ( MAX ⁇ ( ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ amin ⁇ present ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ a ⁇ , ⁇ ⁇ ⁇ Gy ⁇ ⁇ amin ⁇ present ⁇ ⁇ ⁇ ⁇ ⁇ Gy ⁇ ⁇ a ⁇ ) , 1 ) ( 21 )
  • step 120 an adjusted integrated value ⁇ a of yaw rate deviation equivalent value ⁇ bpf and an adjusted integrated value ⁇ Gya of vehicle lateral acceleration Gyftbpf are calculated in accordance with the under-mentioned equations 22 and 23, respectively.
  • ⁇ a present ⁇ a ⁇ Gaj (22)
  • ⁇ Gya present ⁇ Gya ⁇ Gaj (23)
  • step 130 when the vehicle lateral acceleration Gyftbpf is positive, an integrated value ⁇ a of the front wheel steered angle deviation value ⁇ bpf equivalent to yaw rate deviation and an integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf are calculated in accordance with the under-mentioned equations 24 and 25, respectively.
  • ⁇ a present ⁇ a+ ⁇ bpf (24)
  • ⁇ Gya present ⁇ Gya+Gyftbpf (25)
  • step 140 the integrated value ⁇ a of the yaw rate deviation equivalent value ⁇ bpf is divided by the integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf to calculate a ratio ⁇ a/ ⁇ Gya of the integrated values.
  • step 150 an estimated value of stability factor Kh is calculated in accordance with the under-mentioned equation 28 in which the designed value Khde in the above-mentioned equation 15 is set to the initial value Kh 0 .
  • Kh Kh 0+( ⁇ a/ ⁇ Gya )/ L (28)
  • step 160 a first order low-pass filter procedure is conducted on the estimated value of stability factor Kh in accordance with the under-mentioned equation 29 having a cut-off frequency Tc set to 0.05 Hz, for example, to calculate a low-pass filtered estimated value Khlpf of stability factor Kh.
  • step 160 a first order low-pass filter procedure is conducted on the absolute value of the difference between the estimated value of stability factor Kh and the low-pass filtered estimated value Khlpf of stability factor Kh in accordance with the under-mentioned equation 30 to calculate a deviation ⁇ Khlpf of the low-pass filtered estimated value of stability factor Kh. Further, an inverse number 1/ ⁇ Khlpf of the deviation ⁇ Khlpf is calculated as a convergence degree Ckh of the estimated value of stability factor Kh.
  • step 170 the reference value ⁇ o for vehicle motion control conducted based on the deviation between a detected yaw rate ⁇ and a target yaw rate ⁇ tt is calculated according to the map corresponding to FIG. 3 on the basis of the convergence degree Ckh of the estimated value of stability factor Kh, whereby a dead zone of vehicle motion control is variably set.
  • step 180 a decision is made as to whether or not the estimated value of stability factor Kh is permitted to be stored in the EEPROM by deciding whether or not the convergence degree Ckh of the estimated value of stability factor Kh is larger than a reference value (a positive value). If a negative decision is made, the control returns to step 20 . If a positive decision is made, in step 190 , the estimated value of stability factor Kh is stored in the EEPROM so as to renew the estimated value of stability factor Kh stored in the EEPROM.
  • step 40 a steady-state standard yaw rate ⁇ t is calculated and in step 60 , a transient yaw rate ⁇ tr is calculated on the basis of the steady-state standard yaw rate ⁇ t.
  • step 70 a first order delay filtered vehicle lateral acceleration Gyft is calculated and in step 80 , an equivalent value ⁇ converted to steered angle deviation of the front wheels is calculated, the value being derived by converting the deviation between the transient yaw rate ⁇ tr and the actual yaw rate ⁇ to the steered angle deviation of the front wheels.
  • step 90 high-pass filtering procedures are conducted on the first order delay filtered vehicle lateral acceleration Gyft and the front wheel steered angle deviation value ⁇ equivalent to yaw rate deviation to calculate a band-pass filtered vehicle lateral acceleration Gyftbpf and a front wheel steered angle deviation value ⁇ bpf equivalent to band-pass filtered yaw rate deviation which is derived by transferring the magnitude of the difference between a band-pass filtered actual yaw rate ⁇ bpf and a band-pass filtered transient yaw rate ⁇ trbpf to a front wheel steered angle deviation.
  • step 130 an integrated value ⁇ a of the front wheel steered angle deviation value ⁇ bpf equivalent to band-pass filtered yaw rate deviation and an integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf are calculated.
  • step 140 a ratio of the integrated values ⁇ a/ ⁇ Gya is calculated by dividing the integrated value ⁇ a of the yaw rate deviation equivalent value ⁇ bpf by the integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf.
  • an estimated value of stability factor Kh is calculated as a sum of the initial value Kh 0 of stability factor Kh and an adjusting value based on the ratio of the integrated values ⁇ a/ ⁇ Gya.
  • an estimated value of stability factor Kh can be calculated as a value which is derived by adjusting the initial value of stability factor utilized in calculation of the steady-state standard yaw rate ⁇ t of the vehicle on the basis of the relationship between the yaw rate deviation and the vehicle lateral acceleration so that a transient yaw rate ⁇ tr of the vehicle approaches a real yaw rate. Accordingly, an estimated value of stability factor can be adjusted so that the estimated value of stability factor approaches a real yaw rate, which enables to derive an estimated value of stability factor which is close to a real stability factor.
  • a steady-state standard yaw rate ⁇ t is calculated on the basis of steering angle ⁇ , etc. which are low-pass filtered in step 30 .
  • step 90 high-pass filtering procedures are conducted on the vehicle lateral acceleration Gyft and the front wheel steered angle deviation value ⁇ equivalent to yaw rate deviation to calculate a band-pass filtered vehicle lateral acceleration Gyftbpf and a front wheel steered angle deviation value ⁇ bpf equivalent to band-pass filtered yaw rate deviation.
  • step 130 an integrated value ⁇ a of the front wheel steered angle deviation value ⁇ bpf equivalent to yaw rate deviation and an integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf are calculated, and in step 140 , a ratio of the integrated values ⁇ a/ ⁇ Gya is calculated.
  • a stability factor Kh can more accurately be estimated as compared with a case where no high-pass filtering procedure is conducted.
  • the number of high-pass filtering procedures can be reduced so that calculation load on the electronic control unit 30 can be alleviated as compared with a case where high-pass filtering procedures are conducted on steering angle ⁇ and lateral acceleration Gy which are used to calculate a steady-state standard yaw rate ⁇ t.
  • band-pass filtering procedures may be conducted on a vehicle lateral acceleration Gy and a front wheel steered angle deviation value ⁇ equivalent to yaw rate deviation without conducting low-pass filtering procedures on steering angle ⁇ , etc.
  • the number of calculations required for filtering procedures can be reduced as compared with the above-mentioned first embodiment while accurately estimating a stability factor Kh and effectively removing high frequency noise so that calculation load on the electronic control unit 30 can further be alleviated.
  • a ratio of the integrated values ⁇ a/ ⁇ Gya is calculated which is utilized to calculate an adjusting value for adjusting the initial value Kh 0 of stability factor Kh which is utilized in calculation of a steady-state standard yaw rate ⁇ t on the basis of an integrated value ⁇ Gya of a band-pass filtered vehicle lateral acceleration Gyftbpf and an integrated value ⁇ a of a band-pass filtered front wheel steered angle deviation value ⁇ bpf equivalent to yaw rate deviation.
  • integrated value ⁇ Gya is calculated as the integrated value of front wheel steered angle deviation value ⁇ equivalent to yaw rate deviation in which the deviation between a transient yaw rate ⁇ tr and an actual yaw rate ⁇ is transferred to the steered angle deviation of the front wheels.
  • stability factor Kh can be estimated without being influenced by vehicle speed V. Therefore, stability factor Kh can accurately be estimated as compared with the case where an integrated value of index values of yaw rate deviation is, for example, an integrated value of the deviation between a transient yaw rate ⁇ tr and an actual yaw rate ⁇ . It is also possible to avoid cumbersome procedures to estimate stability factor Kh for each vehicle speed V or to change stability factor Kh used to calculate a target yaw rate ⁇ tt for each vehicle speed V to thereby reduce the number of required calculations and the capacity of storing device.
  • step 110 a decision is made as to whether or not adjustments are to be executed on the integrated values ⁇ a of the band-pass filtered yaw rate deviation equivalent value ⁇ bpf converted to steered angle deviation of the front wheels and the present integrated values ⁇ Gya of the band-pass filtered vehicle lateral acceleration Gyftbpf. If a positive decision is made, an adjust gain Gaj which is not larger than 1 is calculated in step 120 . In step 130 , an integrated value ⁇ a of the front wheel steered angle deviation value ⁇ bpf equivalent to yaw rate deviation and an integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf are calculated as integrated values which are adjusted with the adjust gain Gaj.
  • an adjust gain Gaj is calculated in accordance with the under-mentioned equation 21 on the basis of the integrated values ⁇ a of the yaw rate deviation equivalent value ⁇ bpf converted to steered angle deviation of the front wheels and the integrated values ⁇ Gya of the vehicle lateral acceleration Gyftbpf. Accordingly, an adjust gain Gaj can be variably set in accordance with the magnitude of the integrated values ⁇ a of the yaw rate deviation equivalent value ⁇ bpf converted to steered angle deviation of the front wheels and the magnitude of the integrated values ⁇ Gya of the vehicle lateral acceleration Gyftbpf.
  • the risk can be reduced that an error in estimating stability factor Kh becomes large for the reason that the adjust gain Gaj is too large, while on the other hand, the risk can as well be reduced that S/N ratio in estimating stability factor Kh decreases for the reason that the adjust gain Gaj is too small.
  • step 180 a decision is made as to whether or not the estimated value of stability factor Kh is permitted to be stored and if a positive decision is made, in step 190 , the estimated value of stability factor Kh is stored in the EEPROM. Therefore, the estimated value of stability factor Kh can be stored in the EEPROM at a stage when the estimated value of stability factor Kh substantially conforms to an actual stability factor. That is, it is possible to repeat to estimate stability factor Kh until the estimated value of stability factor Kh substantially conforms to an actual stability factor to thereby gradually make the estimated value of stability factor Kh be closer to an actual stability factor.
  • step 100 a decision is made as to whether or not the vehicle is under the turn running condition and if a positive decision is made, the control procedures of step 110 and the following steps are executed. Therefore, it is possible to prevent step 110 and the following steps from being unnecessarily conducted and stability factor Kh from being inaccurately estimated under a situation where the vehicle is not turning and accordingly accurate estimation of t stability factor Kh is impossible.
  • step 160 a deviation ⁇ Khlpf of the low-pass filtered estimated value of stability factor Kh is calculated and an inverse number1/ ⁇ Khlpf of the deviation ⁇ Khlpf is calculated as a convergence degree Ckh of the estimated value of stability factor Kh.
  • step 170 the reference value ⁇ o for vehicle motion control conducted based on the yaw rate deviation ⁇ so that as the convergence degree Ckh increases, the reference value ⁇ o decreases, whereby a dead zone of vehicle motion control is variably set.
  • the reference value ⁇ o can be enlarged to extend the dead zone of the vehicle motion control and the inaccurate vehicle motion control can be prevented from being conducted with a control amount based on inaccurate estimated value of stability factor Kh.
  • the reference value ⁇ o can be reduced to narrow the dead zone of the vehicle motion control and the accurate vehicle motion control can be conducted with a control amount based on accurate estimated value of stability factor Kh.
  • FIG. 4 is a flowchart showing a main portion of a routine for calculating a stability factor Kh by estimation in a second embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • steps identical to those shown in FIG. 2 are denoted by the same step numbers. The same goes in the flowcharts for the embodiments described hereinafter.
  • step 80 the number of reciprocating steering operations by a driver per unit time is calculated as steering frequency fs in step 82 .
  • a cutoff frequency fhc of a high-pass filtering procedure in step 90 is also calculated on the basis of the steering frequency fs from a map corresponding to the graph shown in FIG. 5 so that as the steering frequency fs decreases, the cutoff frequency fhc lowers.
  • cutoff frequency is set to the cutoff frequency fhc calculated in step 82 .
  • the cutoff frequency fhc of a high-pass filtering procedure in step 90 is constant. Accordingly, if the cutoff frequency fhc is set so high that the influence of zero point offset in the sensors may surely be removed, there arises a risk that stability factor Kh can not be estimated under a situation where the number of reciprocating steering operations by a driver per unit time is small. In contrast, if the cutoff frequency fhc is set so low, there arises a risk that the adverse influence of zero point offset in the sensors can not be removed under a situation where the number of reciprocating steering operations by a driver per unit time is large.
  • the cutoff frequency fhc is variably set in accordance with steering frequency fs so that as the steering frequency fs is lower, the cutoff frequency fhc lowers. Therefore, estimation of stability factor Kh can be prevented from being defied under a situation where the number of reciprocating steering operations by a driver per unit time is small while effectively removing the influence of zero point offset in the sensors under a situation where the number of reciprocating steering operations by a driver per unit time is large.
  • cutoff frequency fhc is calculated on the basis of the steering frequency fs from the map, it may be calculated by a function of the steering frequency fs.
  • FIG. 5 is a flowchart showing a main portion of a routine for calculating a stability factor Kh by estimation in a third embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • step 80 the number of reciprocating steering operations by a driver per unit time is calculated as steering frequency fs in step 84 .
  • a cutoff frequency fhc of a high-pass filtering procedure is also calculated on the basis of the steering frequency fs and longitudinal acceleration Gx of the vehicle from a map corresponding to the graph shown in FIG. 7 so that as the steering frequency fs decreases, the cutoff frequency fhc lowers and as the absolute value of longitudinal acceleration Gx of the vehicle increases, the cutoff frequency fhc also increases.
  • cutoff frequency is set to the cutoff frequency fhc calculated in step 84 .
  • the influence of zero point offset in the sensors is the second to the fourth terms in by the above-mentioned equation 17, that is, “ ⁇ 0 ⁇ KhdeGy 0 L ⁇ 0 L/V”. Therefore, as the change in vehicle speed V is larger, that is, as the magnitude of longitudinal acceleration Gx of the vehicle is larger, the influence of zero point offset in the sensors against the change of steady-state standard yaw rate ⁇ t increases and, to the contrary, as the magnitude of longitudinal acceleration Gx of the vehicle is lower, the influence of zero point offset in the sensors against the change of steady-state standard yaw rate ⁇ t decreases.
  • the cutoff frequency fhc is variably set as well in accordance with longitudinal acceleration Gx of the vehicle so that as the absolute value of longitudinal acceleration Gx of the vehicle is higher, the cutoff frequency fhc of a high-pass filtering procedure increases. Therefore, it is possible not only to achieve the same operation and effect as in the second embodiment, but also to effectively remove the influence of zero point offset in the sensors regardless of the change in vehicle speed V.
  • cutoff frequency fhc is calculated on the basis of the steering frequency fs and the absolute value of longitudinal acceleration Gx of the vehicle from the map, it may be calculated by a function of the steering frequency fs and the absolute value of longitudinal acceleration Gx of the vehicle.
  • FIG. 8 is a flowchart showing a main portion of a routine for calculating a stability factor Kh by estimation in a fourth embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • step 105 is conducted prior to step 110 .
  • step 105 a decision is made as to whether or not the vehicle is under the condition that allows to estimate a stability factor Kh with high reliability. If a negative decision is made, the control returns to step 20 . If a positive decision is made, the control proceeds to step 110 .
  • condition B1 is based on the consideration that at a rough road, actual yaw rate ⁇ includes noise and tire grip to road surface may fluctuate.
  • condition B2 is based on the consideration that in the calculation of steady-state standard yaw rate ⁇ t according to the above-mentioned equation 11, no influence of braking force is presupposed.
  • stability factor Kh can more accurately be estimated as compared with the first to third embodiments in which a decision is not conducted as to whether or not the vehicle is under the condition that allows estimation of a stability factor Kh with high reliability.
  • FIGS. 9 and 10 are flowcharts showing a main portion of the former half and the latter half, respectively, of a routine for calculating a stability factor Kh by estimation in a fifth embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • step 70 a decision is made as to whether or not the vehicle is under clockwise turning condition in step 72 . If a positive decision is made, in steps 80 - 190 , the control procedures same as in steps 80 - 190 in the first embodiment are executed for clockwise turning of the vehicle. To the contrary, if a negative decision is made, in steps 85 - 195 , the control procedures same as in steps 80 - 190 in the first embodiment are executed for counter-clockwise turning of the vehicle.
  • a yaw rate deviation equivalent value ⁇ r converted to steered angle deviation is calculated in accordance with the under-mentioned equation 31 which corresponds to the above-mentioned equation 20, the value being derived for the clockwise turn of the vehicle by converting the deviation between the band-pass filtered actual yaw rate ⁇ rbpf and the band-pass filtered transient yaw rate ⁇ trrbpf to the steered angle deviation of the front wheels.
  • step 90 high-pass filtering procedures are conducted on the first order delay filtered vehicle lateral acceleration Gyft which was calculated in step 70 and the equivalent value ⁇ r converted to steered angle deviation of the front wheels which was calculated in step 80 to remove influences due to zero point offset in the sensors.
  • the high-pass filtering procedure may as well be, for example, a first-order high-pass filtering having a cut-off frequency of 0.2 Hz.
  • the vehicle lateral acceleration Gyft and the yaw rate deviation equivalent value ⁇ r converted to steered angle deviation of the front wheels which were high-pass filtered in step 90 are referred to a band-pass filtered vehicle lateral acceleration Gyftbpf and a band-pass filtered yaw rate deviation equivalent value ⁇ rbpf converted to steered angle deviation of the front wheels.
  • step 110 a decision is made as to whether or not adjustments are to be executed on the present integrated values ⁇ ra of the band-pass filtered yaw rate deviation equivalent value ⁇ rbpf converted to steered angle deviation of the front wheels and the present integrated values ⁇ Gya of the band-pass filtered vehicle lateral acceleration Gyftbpf calculated in step 130 in previous cycle. If a negative decision is made, the control proceeds to step 130 , while a positive decision is made, the control proceeds to step 120 .
  • a decision may be made that adjustments are to be executed on the integrated values ⁇ ra and ⁇ Gya when either of the under-mentioned (A1r) and (A2r) is satisfied.
  • the condition (A2r) is decided whether or not it is satisfied when a time constant coefficient Tp of steering response is estimated and a time constant coefficient Tpr of steering response is se to the estimated value in step 50 .
  • step 120 an adjust gain Gajr for clockwise turning is calculated in accordance with the under-mentioned equation 32 which corresponds to the above-mentioned equation 21.
  • Gajr MIN ⁇ ( MAX ⁇ ( ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ amin ⁇ present ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ra ⁇ , ⁇ ⁇ ⁇ Gy ⁇ ⁇ amin ⁇ present ⁇ ⁇ ⁇ ⁇ ⁇ Gy ⁇ ⁇ a ⁇ ) , 1 ) ( 32 )
  • step 120 an adjusted integrated value ⁇ ra of yaw rate deviation equivalent value ⁇ rbpf and an adjusted integrated value ⁇ Gya of vehicle lateral acceleration Gyftbpf are calculated in accordance with the under-mentioned equations 33 and 34, respectively.
  • ⁇ ra present ⁇ ra ⁇ Gajr (33)
  • ⁇ Gya present ⁇ Gya ⁇ Gajr (34)
  • step 130 when the vehicle lateral acceleration Gyftbpf is positive, an integrated value ⁇ ra of the front wheel steered angle deviation value ⁇ rbpf equivalent to yaw rate deviation and an integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf are calculated in accordance with the under-mentioned equations 35 and 36, respectively.
  • ⁇ ra present ⁇ ra+ ⁇ rbpf (35)
  • ⁇ Gya present ⁇ Gya+Gyftbpf (36)
  • an integrated value ⁇ ra of the yaw rate deviation equivalent value ⁇ rbpf and an integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf are calculated in accordance with the under-mentioned equations 37 and 38, respectively.
  • ⁇ ra present ⁇ ra ⁇ rbpf (37)
  • ⁇ Gya present ⁇ Gya ⁇ Gyftbpf (38)
  • step 140 the integrated value ⁇ ra of the yaw rate deviation equivalent value ⁇ rbpf is divided by the integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf to calculate a ratio of the integrated values ⁇ ra/ ⁇ Gya.
  • step 150 an estimated value of stability factor Khr for clockwise turning is calculated in accordance with the under-mentioned equation 39 which corresponds to the above-mentioned equation 28.
  • Khr Kh 0+( ⁇ ra/ ⁇ Gya )/ L (39)
  • step 160 a first order low-pass filter procedure is conducted on the estimated value of stability factor Khr in accordance with the under-mentioned equation 40 which corresponds to the above-mentioned equation 29.
  • Khrlpf 1 1 + sTc ⁇ Khr ( 40 )
  • step 160 a first order low-pass filter procedure is conducted on the absolute value of the difference between the estimated value of stability factor Khr and the low-pass filtered estimated value Khrlpf of stability factor Khr in accordance with the under-mentioned equation 41 to calculate a deviation ⁇ Khrlpf of the low-pass filtered estimated value of stability factor Khr. Further, an inverse number1/ ⁇ Khrlpf of the deviation ⁇ Khrlpf is calculated as a convergence degree Ckhr of the estimated value of stability factor Khr for clockwise turning. That is, a convergence degree Ckhr of the estimated value of stability factor Khr for clockwise turning is calculated in accordance with the under-mentioned equation 42.
  • a target yaw rate ⁇ ttr for clockwise turning which corresponds to the transient yaw rate ⁇ tr is calculated and the deviation between a detected yaw rate ⁇ and the target yaw rate ⁇ ttr is calculated as a yaw rate deviation ⁇ r.
  • the reference value ⁇ ro for vehicle motion control during clockwise turning based on the yaw rate deviation ⁇ r is calculated according to the map similar to FIG. 3 on the basis of the convergence degree Ckhr of the stability factor, whereby a dead zone of vehicle motion control is variably set for clockwise turning.
  • step 180 a decision is made as to whether or not the estimated value of stability factor Khr is permitted to be stored in the EEPROM by deciding whether or not the convergence degree Ckhr of the stability factor is larger than a reference value (a positive value). If a negative decision is made, the control returns to step 20 . If a positive decision is made, in step 190 , the estimated value of stability factor Khr is stored in the EEPROM so as to renew the estimated value of stability factor Khr stored in the EEPROM.
  • steps 85 - 195 the control procedures same as in steps 80 - 190 are executed for counter-clockwise turning of the vehicle by displacing “r” indicating clockwise turning with “l” indicating counter-clockwise turning.
  • Turning characteristic for clockwise turning and turning characteristic for counter-clockwise turning may be different from each other.
  • turning characteristic differs according to turning direction of the vehicle.
  • the fifth embodiment it is possible not only to achieve the same operation and effect as in the first embodiment, but also, for the reason that a time constant coefficient of steering response is estimated for each turning direction, to estimate stability factors Khr and Khl for both clockwise turning and counter-clockwise turning with high reliability even when turning characteristic differs according to turning direction of the vehicle.
  • FIGS. 11 and 12 are flowcharts showing a main portion of the former half and the latter half, respectively, of a routine for calculating a stability factors Kh by estimation in a sixth embodiment of the turning characteristic estimation device according to the present invention which is configured as a modification of the first embodiment.
  • step 74 a decision is made as to whether or not the absolute value of lateral acceleration Gy of the vehicle is larger than a first reference value Gy 1 (a positive constant). If a negative decision is made, the control returns to step 20 . If a positive decision is made, the control proceeds to step 76 .
  • step 76 a decision is made as to whether or not the absolute value of lateral acceleration Gy of the vehicle is larger than a second reference value Gy 2 (a positive constant larger than the first reference value Gy 1 ). If a negative decision is made, in steps 80 - 190 , the control procedures same as in steps 80 - 190 in the first embodiment are executed for the case where the absolute value of lateral acceleration Gy of the vehicle is larger than the first reference value Gy 1 and smaller than the second reference value Gy 2 (a first area of lateral acceleration Gy).
  • steps 85 - 195 the control procedures same as in steps 80 - 190 in the first embodiment are executed for the case where the absolute value of lateral acceleration Gy of the vehicle is larger than the second reference value Gy 2 (a second area of lateral acceleration Gy).
  • a yaw rate deviation equivalent value ⁇ 1 converted to steered angle deviation is calculated in accordance with the under-mentioned equation 43 which corresponds to the above-mentioned equation 20, the value being derived for the first area of lateral acceleration Gy by converting the deviation between the band-pass filtered actual yaw rate ⁇ rbpf and the band-pass filtered transient yaw rate ⁇ tr 1 bpf to the steered angle deviation of the front wheels.
  • ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ 1 ( ⁇ ⁇ ⁇ tr ⁇ ⁇ 1 ⁇ bpf - ⁇ ⁇ ⁇ 1 ⁇ bpf ) ⁇ L V ( 43 )
  • step 90 high-pass filtering procedures are conducted on the first order delay filtered vehicle lateral acceleration Gyft which was calculated in step 70 and the equivalent value ⁇ 1 converted to steered angle deviation of the front wheels which was calculated in step 80 to remove influences due to zero point offset in the sensors.
  • the high-pass filtering procedure may as well be, for example, a first-order high-pass filtering having a cut-off frequency of 0.2 Hz.
  • the vehicle lateral acceleration Gyft and the yaw rate deviation equivalent value ⁇ 1 converted to steered angle deviation of the front wheels which were high-pass filtered in step 90 are referred to a band-pass filtered vehicle lateral acceleration Gyftbpf and a band-pass filtered yaw rate deviation equivalent value ⁇ 1 bpf converted to steered angle deviation of the front wheels.
  • step 110 a decision is made as to whether or not adjustments are to be executed on the present integrated values ⁇ r 1 of the band-pass filtered yaw rate deviation equivalent value ⁇ 1 bpf converted to steered angle deviation of the front wheels and the present integrated values ⁇ Gya of the band-pass filtered vehicle lateral acceleration Gyftbpf calculated in step 130 in previous cycle. If a negative decision is made, the control proceeds to step 130 , while a positive decision is made, the control proceeds to step 120 .
  • a decision may be made that adjustments are to be executed on the integrated values ⁇ 1 a and ⁇ Gya when either of the under-mentioned (A11) and (A21) is satisfied.
  • the condition (A21) is decided whether or not it is satisfied when a time constant coefficient Tp of steering response is estimated and a time constant coefficient Tp 1 of steering response is se to the estimated value in step 50 .
  • step 120 an adjust gain Gaj 1 for the first area of lateral acceleration Gy is calculated in accordance with the under-mentioned equation 44 which corresponds to the above-mentioned equation 21.
  • Gaj ⁇ ⁇ 1 MIN ⁇ ( MAX ⁇ ( ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ amin ⁇ present ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ ⁇ 1 ⁇ a ⁇ , ⁇ ⁇ ⁇ Gy ⁇ ⁇ amin ⁇ present ⁇ ⁇ ⁇ ⁇ ⁇ Gy ⁇ ⁇ a ⁇ ) , 1 ) ( 44 )
  • step 120 an adjusted integrated value ⁇ 1 a of yaw rate deviation equivalent value ⁇ 1 bpf and an adjusted integrated value ⁇ Gya of vehicle lateral acceleration Gyftbpf are calculated in accordance with the under-mentioned equations 45 and 46, respectively.
  • ⁇ 1 a present ⁇ 1 a ⁇ Gaj 1 (45)
  • ⁇ Gya present ⁇ Gya ⁇ Gaj 1 (46)
  • step 130 when the vehicle lateral acceleration Gyftbpf is positive, an integrated value ⁇ 1 a of the front wheel steered angle deviation value ⁇ 1 bpf equivalent to yaw rate deviation and an integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf are calculated in accordance with the under-mentioned equations 47 and 48, respectively.
  • ⁇ 1 a present ⁇ 1 a+ ⁇ 1 bpf (47)
  • ⁇ Gya present ⁇ Gya+Gyftbpf (48)
  • an integrated value ⁇ 1 a of the yaw rate deviation equivalent value ⁇ 1 bpf and an integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf are calculated in accordance with the under-mentioned equations 49 and 50, respectively.
  • ⁇ 1 a present ⁇ 1 a ⁇ 1 bpf (49)
  • ⁇ Gya present ⁇ Gya ⁇ Gyftbpf (50)
  • step 140 the integrated value ⁇ 1 a of the yaw rate deviation equivalent value ⁇ 1 bpf is divided by the integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf to calculate a ratio of the integrated values ⁇ 1 a / ⁇ Gya.
  • step 150 an estimated value of stability factor Khr for the first area of lateral acceleration Gy is calculated in accordance with the under-mentioned equation 51 which corresponds to the above-mentioned equation 28.
  • Kh 1 Kh 0+( ⁇ 1 a/ ⁇ Gya )/ L (51)
  • step 160 a first order low-pass filter procedure is conducted on the estimated value of stability factor Kh 1 in accordance with the under-mentioned equation 52 which corresponds to the above-mentioned equation 29.
  • Khrlpf 1 1 + sTc ⁇ Kh ⁇ ⁇ 1 ( 52 )
  • step 160 a convergence degree Ckh 1 of the estimated value of stability factor Kh 1 for the first area of lateral acceleration Gy is calculated in accordance with the under-mentioned equation 53 which corresponds to the above-mentioned equation 42.
  • Ckh 1 (1 +sTc )/( Kh 1 ⁇ Kh 1 lpf ) (53)
  • a target yaw rate ⁇ ttr for the first area of lateral acceleration Gy is calculated and the deviation between a detected yaw rate ⁇ and the target yaw rate ⁇ tt 1 is calculated as a yaw rate deviation ⁇ 1 .
  • the reference value ⁇ 1 o for vehicle motion control during clockwise turning based on the yaw rate deviation ⁇ 1 is calculated according to the map similar to FIG. 3 on the basis of the convergence degree Ckh 1 of the stability factor, whereby a dead zone of vehicle motion control is variably set for the first area of lateral acceleration Gy.
  • step 180 a decision is made as to whether or not the estimated value of stability factor Kh 1 is permitted to be stored in the EEPROM by deciding whether or not the convergence degree Ckh 1 of the stability factor is larger than a reference value (a positive value). If a negative decision is made, the control returns to step 20 . If a positive decision is made, in step 190 , the estimated value of stability factor Kh 1 is stored in the EEPROM so as to renew the estimated value of stability factor Kh 1 stored in the EEPROM.
  • steps 85 - 195 the control procedures same as in steps 80 - 190 are executed for the second area of lateral acceleration Gy by displacing “1” indicating the first area of lateral acceleration Gy with “2” indicating the second area of lateral acceleration Gy.
  • turning characteristic may change according to the magnitude of lateral acceleration Gy.
  • FIG. 13 is a flowchart showing a main portion of a routine for calculating a stability factor Kh by estimation in a seventh embodiment of the turning characteristic estimation device according to the present invention.
  • steps 121 - 126 shown in FIG. 13 are executed in place of step 120 in the first embodiment.
  • step 121 lower limit values ⁇ amink and ⁇ Gyamink of the integrated values are calculated from maps corresponding to the graphs shown in FIGS. 14 and 15 , respectively, on the basis of the absolute value of the deviation ⁇ Kh of stability factor.
  • step 122 lower limit values ⁇ amint and ⁇ Gyamint of the integrated values are calculated from maps corresponding to the graphs shown in FIGS. 16 and 17 , respectively, on the basis of the absolute value of the deviation ⁇ Tp of time constant coefficient of steering response.
  • a lower limit value ⁇ amin of the integrated values is set to larger one of the lower limit value ⁇ amink of the integrated value based on the absolute value of the deviation ⁇ Kh of stability factor and the lower limit value ⁇ amint of the integrated value based on the absolute value of the deviation ⁇ Tp of time constant coefficient of steering response.
  • a lower limit value ⁇ Gyamin of the integrated values is set to larger one of the lower limit value ⁇ Gyamink of the integrated value based on the absolute value of the deviation ⁇ Kh of stability factor and the lower limit value ⁇ Gyamint of the integrated value based on the absolute value of the deviation ⁇ Tp of time constant coefficient of steering response.
  • step 125 an adjusting gain Gaj is calculated in accordance with the above-mentioned equation 21 on the basis of the lower limit values ⁇ amin and ⁇ Gyamin of the integrated values.
  • step 126 an adjusted integrated value ⁇ a of yaw rate deviation equivalent value ⁇ bpf and an adjusted integrated value ⁇ Gya of vehicle lateral acceleration Gyftbpf are calculated in accordance with the above-mentioned equations 22 and 23, respectively.
  • an adjust gain Gaj for adjusting the integrated values ⁇ a and ⁇ Gya is calculated in accordance with the equation 21 in which the lower limit values ⁇ amin and ⁇ Gyamin are constant. Accordingly, if the lower limit values ⁇ amin and ⁇ Gyamin are set to small values so that the integrated values ⁇ a and ⁇ Gya are reliably decreased, there arises a risk that the integrated values Ma and ⁇ Gya are excessively decreased under the situation where the deviation ⁇ Kh of stability factor and the deviation ⁇ Tp of time constant coefficient of steering response are small in magnitude.
  • the lower limit values ⁇ amin and ⁇ Gyamin of the integrated values are variably be set in accordance with the magnitude of the deviation ⁇ Kh of stability factor and the deviation ⁇ Tp of time constant coefficient of steering response so that when the deviation ⁇ Kh of stability factor and the deviation ⁇ Tp of time constant coefficient of steering response are large in magnitude, the lower limit values ⁇ amin and ⁇ Gyamin of the integrated values are smaller as compared with the case where the deviation ⁇ Kh of stability factor and the deviation ⁇ Tp of time constant coefficient of steering response are small in magnitude.
  • the risk can be reduced that the integrated values ⁇ a and ⁇ Gya are excessively decreased under the situation where the deviation ⁇ Kh of stability factor and the deviation ⁇ Tp of time constant coefficient of steering response are small in magnitude.
  • the integrated values ⁇ a and ⁇ Gya can sufficiently be decreased and the influences by the previous integrated values ⁇ a and ⁇ Gya can effectively be reduced under the situation where the deviation ⁇ Kh of stability factor and the deviation ⁇ Tp of time constant coefficient of steering response are large in magnitude.
  • a lower limit value ⁇ amin of the integrated values is set to larger one of the lower limit value ⁇ amink of the integrated value and the lower limit value ⁇ amint of the integrated value
  • a lower limit value ⁇ Gyamin of the integrated values is set to larger one of the lower limit value ⁇ Gyamink of the integrated value and the lower limit value ⁇ Gyamint of the integrated value.
  • S/N ratio in estimating stability factor can be enhanced as compared with the case where a lower limit value ⁇ amin of the integrated values is set to smaller one of the lower limit value ⁇ amink of the integrated value and the lower limit value ⁇ amint of the integrated value, and a lower limit value ⁇ Gyamin of the integrated values is set to smaller one of the lower limit value ⁇ Gyamink of the integrated value and the lower limit value ⁇ Gyamint of the integrated value.
  • lower limit values of the integrated values may be set to smaller one ro the average of the associated lower limit values of the integrated values.
  • lower limit values ⁇ mink and ⁇ Gyamink of the integrated values are calculated from the maps on the basis of the absolute value of the deviation ⁇ Kh of stability factor
  • lower limit values ⁇ amint and ⁇ Gyamint of the integrated values are calculated from the maps on the basis of the absolute value of the deviation ⁇ Tp of time constant coefficient of steering response, they may be calculated by a function of the absolute value of the deviation ⁇ Kh of stability factor and the absolute value of the deviation ⁇ Tp of time constant coefficient of steering response, respectively.
  • step 160 a convergence degree of the estimated value of stability factor is calculated and in step 170 , a dead zone of vehicle motion control is variably set in accordance with the convergence degree.
  • variable setting of a dead zone of vehicle motion control in accordance with the convergence degree may be omitted.
  • step 80 an equivalent value converted to steered angle deviation of the front wheels is calculated which is derived by converting the deviation between the transient yaw rate ⁇ tr and the actual yaw rate ⁇ to the steered angle deviation of the front wheels.
  • a high-pass filtering procedure may be conducted on the deviation between the transient yaw rate ⁇ tr and the actual yaw rate ⁇ to calculate a band-pass filtered yaw rate deviation ⁇ bpf; a ratio of the yaw rate deviation ⁇ bpf relative to the integrated value ⁇ Gya of the vehicle lateral acceleration Gyftbpf may be calculated in place of the ratio of the integrated values ⁇ a/ ⁇ Gya; and an estimated value of stability factor Kh may be calculated in accordance with the under-mentioned equation 54 on the basis of the ratio of the integrated values ⁇ bpf/ ⁇ Gya.
  • Kh Kh 0+( ⁇ bpf/ ⁇ Gya )/ L (54)
  • an estimated value of stability factor Kh is calculated in accordance with the equation 54, it is preferable to set a plurality of vehicle speed areas and to calculate estimated value of stability factor for each vehicle speed area. It is also preferable to calculate convergence degree of estimated value of stability factor for each vehicle speed area and to set a dead zone of vehicle motion control for each vehicle speed area. Further, it is preferable to set stability factor Kh which is used to calculate a target yaw rate in vehicle motion control to an estimated value for each vehicle speed area.
  • an adjust gain Gaj is calculated to larger one of the first gain ( ⁇ amin/
  • one of the first and the second gain may be omitted and the other of the first and the second gain may be set to an adjust gain Gaj.
  • stability factor Kh is estimated for the first and second areas having different lateral acceleration Gy in magnitude.
  • stability factor Kh may be estimated for three or more areas having different lateral acceleration Gy in magnitude.
  • the configuration of the fifth or sixth embodiment may be adapted to any one of the second to forth embodiments.
  • the above-described seventh embodiment is configured as a modification of the first embodiment, the configuration of the seventh embodiment may be adapted to any one of the second to sixth embodiments.
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EP2481651A1 (en) 2012-08-01
EP2481651A4 (en) 2016-10-19
US20120173040A1 (en) 2012-07-05
JP5024456B2 (ja) 2012-09-12
CN102548824A (zh) 2012-07-04

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